Trans control relay needed?

[plagee]

What in the world does the trans control relay do? I have the part numnber of 3990842 (littlefuse). It has a seperate harness that connects to the main harness above the hood hinge. There is also what appears to be another relay next to it that is connected to the same harness, the ony thing the wiring diagram lists is: RELAY ASM CONT SW. The harness that I have in the truck has 4 wires that have been butchered by the previous owner, and do not connect to anything. Any info would help and would be much appreciated.